Due to a factor of this quantity squared, linear accelerators exhibit negligible radiation loss compared to circular ones. The reciprocal of this quantity gives the approximate width of the radiation cone of a moving particle, and protons can reach higher energies than electrons in circular accelerators due to synchrotron radiation being proportional to this quantity to the (*) fourth power. Two pi times the radius times this quantity equals the circumference of a rigid rotating disk. M c squared times this value equals energy, which also appears in the top left of the boost matrix between collinear reference frames. This quantity is equal to one over the square root (10[1])of the quantity one minus velocity squared over the speed of light squared. For 10 points, name this quantity, denoted gamma, that quantifies the magnitude of time dilation in special relativity. ■END■ (10[1])